Is the decay constant , constant for all isotopes of element

[CivilSigma]

I have this true and false question:

" The half life and therefore the decay constant will be the same for every isotope
a) True
b) False
c) only if it is an isotope of the same element
"

I think this is false, just by intuition.

 

[Simon Bridge]

But you need more than just intuition... how could you check if all isotopes of the same element have the same decay constant?
For instance - can a stable element have radioactive isotopes?

 

[CivilSigma]

Yes they can, I know there is Tritium , an unstable isotope of the stable element Hydrogen.

To check, we can place two samples in a container and monitor their loss of matter, and it should be equal?

 

[Simon Bridge]

Very good... so what is the decay constant for hydrogen?

 

[CivilSigma]

I read that Tritium has half life of 13.2 years, where as deuterium has a halflife of 10.3 minutes. Thank you :)

 

[Simon Bridge]

Even if you didn't know those values, you know that tritium decays and hydrogen does not, so the decay constant for hydrogen (half-life infinity) is not the same as for tritium (half-life finite). This is how you can get needed conclusions from incomplete information.